1. Field of the Invention
The present invention relates to a rechargeable battery and, more particularly, to a rechargeable battery which is not to be detached due to deformation of a molded resin member by strengthening the fixing force of the molded resin member connecting a bare cell with a protection circuit module.
2. Description of the Related Art
In general, a rechargeable battery is a battery which may be used repeatedly by recharging, in contrast with a disposable battery. Rechargeable batteries are used as main power sources of portable devices for communication, information processing and audio/video. In recent years, the rechargeable battery has rapidly developed and prevailed in the industry, since the rechargeable battery is a power source having ultra-lightweight, high energy density, high output voltage, low self-discharge, environmental-friendly battery and long life time.
The rechargeable battery is classified into a nickel-metal hydride (Ni-MH) battery and a lithium ion (Li-ion) battery in accordance with an electrode active material, in particular the lithium ion battery is classified into a liquid electrolyte lithium ion battery, a solid polymer electrolyte lithium ion battery and a gel electrolyte lithium ion battery according to a kind of electrolytes. Also, the rechargeable battery is classified into various kinds of a can-type battery and, a pouch-type battery and other types of batteries according to the shape of a container in which an electrode assembly is accommodated.
It is possible for the lithium ion battery to have ultra-lightweight, because the lithium ion battery has considerably higher energy density than that of the disposable battery. The lithium ion battery has an average voltage of 3.6V per cell, which is three times higher than 1.2 V of a nickel-cadmium battery or a nickel-hydrogen battery, thus the lithium ion battery has three times larger compact effects. Also, the lithium ion battery has advantages that the self-discharge rate of the lithium ion battery is less than 5% per month at 20° C. and this percentage is ⅓ level of the nickel-cadmium battery or the nickel-hydrogen battery, and that the lithium ion battery is an environmental-friendly battery because of not using heavy metals such as Cd or Hg, and that the lithium ion battery may be repeatedly recharged or discharged over 1000 times in the normal state. Therefore, the lithium ion battery has been rapidly developing because of the above described advantages while information & communication technologies have been developing.
A bare cell of a conventional rechargeable battery is formed by providing an electrode assembly composed of an anode plate, a cathode plate and a separator into a can made of aluminum or aluminum alloy, covering an upper opening of the can with a cap assembly, and then injecting the electrolyte therein and sealing the can. When the can is made of Al or Al alloy as described above, the light weight of the battery is achieved due to the aluminum's property and the battery does not corrode even after long periods of use under high voltages.
The sealed bare cell is electrically connected with a protection circuit module, and the protection circuit module is composed of safety devices such as a positive temperature coefficient (PTC) device, a thermal fuse, a protection circuit board, and other battery parts.
Connecting terminals of the protection circuit board are electrically connected with the bare cell through separate lead plates, a cap plate provided in the bare cell is connected to an anode terminal of the protection circuit board by an anode lead plate, and a cathode terminal of the bare cell is connected to a cathode terminal of the protection circuit board by a cathode lead plate.
The bare cell and the protection circuit module, which are electrically connected with each other, are received in a separate hard pack in order to tie-up the connection or form complete external appearance of the rechargeable battery by means of the molded resin member made of a hot melt resin.
On the other hand, if the molded resin member, which binds the bare cell to the protection circuit module electrically connected with the bare cell, is twisted to a certain angle, problems may occur on the electrical connections including the anode and cathode terminals of the bare cell, the lead plates, and the external terminal of the protection circuit board, thus the safety devices of the battery may not operate, even though the molded resin member is not totally broken down.
As described above, when the molded resin member is molded in the shape of pack battery by using the melt resin, the molded resin member is deformed by the twist or bend of the pack relatively compared with the bare cell, thus the molded resin member is detached from the bare cell.